Add docs/guides/editing-hardware-docs.md covering the frontmatter schema,
rack/shelf/PDU/power/network fields, the `make docs-index` workflow and
CI drift gate, plus dos and don'ts. Kept under docs/guides/ so the
hardware generators don't parse it as a host file. Linked under the
Hardware nav section so it publishes to docs.makerfloss.eu.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
